I. Field of the Invention
This invention relates generally to fire fighting equipment, and more particularly to a control system for controlling the addition of a liquid chemical foamant to selected ones of a plurality of water delivery fire hoses such that the concentration of liquid chemical foamant at the discharge end of the fire hoses if maintained at a preset desired value as the water flow rate through the several hoses is made to vary.
II. Discussion of the Prior Art
Fire trucks, fire boats, military equipment and the like used in extinguishing large industrial fires will typically have a plurality of water discharge lines coupled through a manifold to a large capacity mid-ship pump where the discharge lines vary in size from those feeding a water cannon capable of delivering 1,000 gallons-per-minute or more to hand lines used in mopping-up operations that may carry 20 gallons-per-minute or less.
One of the most significant advancement in the filed of fire fighting has come through the use of chemical foamants specifically formulated to augment the fire fighting ability of water. Foam injection systems have been designed to introduce liquid chemical foamant concentrate into a water stream being directed at a fire. A key advantage to using such foams is the dramatic reduction in the time required to extinguish fires. It has been demonstrated that Class A foam is from five to ten more times more effective as a fire suppressant than water alone. Utilizing foam, fires are extinguished faster and with substantially less water damage. The foam proves to be an effective barrier, preventing fire from spreading and protecting adjacent structures. As is set out in the Arvidson et al. U.S. Reissue Pat. No. 35,362, the teachings of which are hereby incorporated by reference, it is desirable to have a foam injection system that is capable of automatically proportioning the foam additive in an exact concentration required for the specific fire-fighting problem, but without overusing and, therefore, wasting the chemical foamant. That patent describes a system that is readily suited to residential fires, automobile fires and those applications where water flow rates tend to be below 1,000 gallons-per-minute. Moreover, the system shown in the aforereferenced Arvidson Reissue Patent accommodates only a single injection point. In that fire vehicles designed for use in fighting large industrial fires may have several discharge lines of varying capacity, a need exists for a foam injection system that permits foam concentrate from a single storage tank to be injected into a plurality of water discharge lines where the water flow rate through the individual lines may vary drastically. For example, one discharge line may be feeding a water cannon while discharge lines are hand lines used in mopping operations.
A need exists for a foam injection system for use with a fire truck or other fire fighting apparatus where there is a plurality of discharge lines downstream from a main water pump. A desirable feature of such a system is to have some or all of the discharge lines capable of flowing a water/foam mixture, or water only, out the nozzle of the discharge lines. It will frequently happen that the foam/water proportioning in each line be different depending upon the type of fire being fought.
The foam proportioning system must also be capable of displaying a variety of parameters to fire-fighting personnel including, but not necessarily limited to, raw water flow rate, total water used, percent of foam concentrate in each of a plurality of water discharge lines, the total amount of concentrate used in all of the lines, a low concentrate supply warning, line pressure readings.